Troubleshooting An E5 Error Code On An Advent Air RV Air Conditioner

Updated 10/18/2025 | Published 03/17/2023

Question:

Hello, controller has been work fine for weeks after installing, but now the controller is constantly flashing E5. Double checked all connection, found no issue with wiring. Any suggestions? P.S. unit was purchased last year from eteailer.com. Thank you

asked by: Guadalupe E

Expert Reply:

For an Advent Air RV Air Conditioner # ACM135 an E5 error typically indicates a communication error between the controller and the thermostat, but it can also indicate an issue with the thermal probe. The thermal probe is typically latched onto the coils up in the condenser unit to detect when they start to freeze to stop and thaw the unit.

The first step is always going to be opening up your air distribution box and checking all connections and the wiring for any damage, which you've stated you've already done. I recommend also checking that probe which should run from the controller to the condenser unit. If it's not in a good spot or the connector to the controller somehow got loose you'd start seeing this error.

If you still can't find the cause of the issue then the controller may be bad. If this is from another system and you just replaced the condenser with the # ACM135 then it may be time to also replace your air distribution box and thermostat with part # ACRG15. This will give you new hardware and mesh better than a mix of different brands.

expert reply by: Kevin C

Alexa H.

9/5/2025

What if it's a whole new system? Everything straight out of the box and it's shooting an E5 error code on the thermostat?

Robert

10/18/2025

Hi Kevin, I’m having a similar problem. My RV has three wires a white, red, and green on the old thermostat. The new thermostat I just bought from you guys the AC TH12P has four post I have the green connected to the comms wire in the Box, the red connected to the 12 V DC and the white two comes be. But I still haven’t E5 error my freezer sensor is connected and I’m a little bit frustrated. Can you help at all?